High-Frequency Module and Method of Manufacturing the Same, and Transmitter, Receiver, Transceiver, and Radar Apparatus Comprising the High-Frequency Module

ABSTRACT

A high-frequency module according to the present embodiment includes a substrate, a circuit board, and a waveguide. The substrate has an input-output portion for high-frequency signals on one surface thereof. The circuit board has a dielectric waveguide line with its end face exposed, and is placed on the one surface of the substrate such that a virtual plane extending beyond the end face is intersected by the one surface of the substrate. The waveguide has openings at ends thereof, in which one of the openings is connected to the end face of the dielectric waveguide line, and the other opening is connected to the input-output portion of the substrate.

TECHNICAL FIELD

The present invention relates to a high-frequency module for use incommunication equipment and a method of manufacturing the high-frequencymodule, and also a transmitter, a receiver, a transceiver, and a radarapparatus comprising the high-frequency module.

BACKGROUND ART

In order to achieve high-speed transmission of large-volume data, therehave been proposed systems based on information-communication equipmentthat utilizes a high-frequency range such as a microwave range of 1 to30 GHz and a millimeter-wave range of 30 to 300 GHz. In addition,millimeter wave-using systems and the like such as a radar apparatusthat measures inter-vehicle distance have been proposed to date.

As a high-frequency circuit board structure adopted in such equipmentutilizing a high-frequency range such as a microwave range and amillimeter-wave range, a monolithic microwave integrated circuit (MMIC)and a structure in which a passive electronic component is mounted on aplanar circuit such as a microstrip line are known. In the planarcircuit, constituent circuits such as a power divider circuit, a branchcircuit, a matching circuit, a hybrid circuit, a filter circuit, and soforth are each put to its proper use to provide a circuit configurationcapable of obtaining desired characteristics meeting systemrequirements.

Moreover, in order to effect radio wave transmission and reception in ahigh-frequency circuit board, an antenna board mounting an antenna isrequired. For connection between the circuit board and the antennaboard, in order to avoid mutual influences of high-frequency signals,the circuit board and the antenna board are commonly constructedindependently of each other, for example, the antenna board is connectedto the back surface of the circuit board. Moreover, in general,input-output ports disposed in the circuit board and the antenna board,respectively, are connected to each other through a waveguide.

For example, in Japanese Unexamined Patent Publication JP-A 2002-84208,there is disclosed a high-frequency module constructed by arranging acircuit board and an antenna board one above the other, interposing awaveguide adaptor between the circuit board and the antenna board, andconnecting an input-output port at a side of the circuit board and aninput-output port at a side of the antenna board to each other through awaveguide formed in the waveguide adaptor.

Moreover, when the input-output port is an opening of a waveguide,connection between the opening and the waveguide is established by amethod of, for example, as disclosed in Japanese Unexamined PatentPublication JP-A 2002-185203, connecting the mutually-correspondingopenings by a solder bump.

Moreover, in Japanese Unexamined Patent Publication JP-A 2004-254068,there is disclosed a high-frequency module in which an input-output portat a side of a circuit board and an input-output port at a side of anantenna board are connected directly to each other by means of a solderbump without using a waveguide adaptor or the like.

However, in the high-frequency modules disclosed in JP-A 2002-84208 andin JP-A 2004-254068, the input-output port at the side of the circuitboard and the input-output port at the side of the antenna board areprovided on the opposed surfaces of the circuit board and the antennaboard, respectively. Therefore, at the time of positioning of theinput-output port and the waveguide or positioning ofmutually-corresponding input-output ports, the input-output port ispoorly visible. This leads to instability in positioning accuracy withconsequent possibility of occurrence of significant positionaldeviation. In the event of such a positional deviation, there may be acase where local transmission-path variations take place at a connectionpart, for example, a transmission path over which a high-frequencysignal is transmitted becomes narrow between the circuit board and theantenna board. In the local area of the transmission path subjected tovariation, reflection of a high-frequency signal or the like occurs,which may give rise to a problem of an increase in transmission loss.Furthermore, the larger is the number of the input-output ports, thelarger is the number of solder bumps which are used for connection ofthe input-output ports, with consequent complication of mounting processsteps.

DISCLOSURE OF INVENTION

An object of the invention is to provide a high-frequency module capableof making high-frequency connection between a circuit board and asubstrate having an input-output portion configured to input and outputhigh-frequency signals stably with lower loss and a method ofmanufacturing a high-frequency module, as well as to provide atransmitter, a receiver, a transceiver, and a radar apparatus comprisingthe high-frequency module.

A high-frequency module in accordance with one embodiment of theinvention comprises a substrate, a circuit board, and a waveguide. Thesubstrate comprises an input-output portion for high-frequency signalsformed on one surface thereof. The circuit board comprises a dielectricwaveguide line with its end face exposed, and is placed on the onesurface of the substrate such that a virtual plane extending beyond theend face is intersected by the one surface of the substrate. Thewaveguide comprises openings at ends thereof. One of the openings isconnected to the end face of the dielectric waveguide line, and theother thereof is connected to the input-output portion of the substrate.

Moreover, a method of manufacturing the high-frequency module inaccordance with one embodiment of the invention comprises a preparationstep, a circuit board placement step, and a waveguide mounting step. Thepreparation step is a step of preparing a substrate, a waveguide, and acircuit board. The substrate comprises an input-output portion forhigh-frequency signals formed on one surface thereof. The waveguidecomprises openings at ends thereof, and has a relationship such that avirtual opening plane extending beyond one of the openings isintersected by a virtual opening plane extending beyond the other of theopenings. The circuit board comprises a dielectric waveguide lineexposed at its end face. The circuit board placement step is a step ofplacing the circuit board at a side of the one surface of the substrate.The waveguide mounting step is a step of mounting the waveguide on thesubstrate such that the one of the openings thereof is connected to theend face of the dielectric waveguide line, and the other of the openingsthereof is connected to the input-output portion of the substrate.

Moreover, a method of manufacturing the high-frequency module inaccordance with another embodiment of the invention comprises apreparation step, a waveguide mounting step, and a circuit boardmounting step. The preparation step is a step of preparing a substrate,a waveguide, and a circuit board. The substrate comprises aninput-output portion for high-frequency signals formed on one surfacethereof. The waveguide comprises openings at ends thereof, and has arelationship such that a virtual opening plane extending beyond one ofthe openings is intersected by a virtual opening plane extending beyondthe other of the openings. The circuit board comprises a dielectricwaveguide line exposed at its end face. The waveguide mounting step is astep of mounting the waveguide on the substrate such that the other ofthe openings is connected to the input-output portion. The circuit boardmounting step is a step of mounting the circuit board on the substratesuch that the end face of the dielectric waveguide line is connected tothe one of the openings of the waveguide.

Moreover, a transmitter in accordance with one embodiment of theinvention comprises the high-frequency module, an oscillator, and anantenna. The oscillator, which is configured to produce a high-frequencysignal, is mounted on the high-frequency circuit board and is connectedto the planar line. The antenna, which is configured to radiate ahigh-frequency signal produced by the oscillator, is disposed at a sideof the other surface of the substrate and is connected to the dielectricwaveguide line.

Moreover, a receiver in accordance with one embodiment of the inventioncomprises the high-frequency module, an antenna, and a wave detector.The antenna, which is configured to acquire a high-frequency signal, isdisposed at a side of the other surface of the substrate and isconnected to the dielectric waveguide line. The wave detector, which isconfigured to detect a high-frequency signal acquired by the antenna, ismounted on the circuit board and is connected to the dielectricwaveguide line.

Moreover, a transceiver in accordance with one embodiment of theinvention comprises the high-frequency module, an oscillator, a branch,a transmitting antenna, a receiving antenna, and a mixer. Theoscillator, which is configured to produce a high-frequency signal, ismounted on the circuit board and is connected to the planar line. Thebranch, which is configured to branch a high-frequency signal producedby the oscillator, is disposed in the planar line. The transmittingantenna, which is configured to radiate one of the high-frequencysignals branched by the branch, is disposed at a side of the othersurface of the substrate and is connected to the dielectric waveguideline. The receiving antenna, which is configured to acquire ahigh-frequency signal, is disposed at the side of the other surface ofthe substrate and is connected to the dielectric waveguide line. Themixer mixes the other of the high-frequency signals branched by thebranch and a high-frequency signal acquired by the receiving antenna andoutputs an intermediate-frequency signal.

Further, a radar apparatus in accordance with one embodiment of theinvention comprises the transceiver and a detector. The detector detectsa distance to an object to be detected or relative velocity on the basisof the intermediate-frequency signal from the mixer.

According to the circuit board of the invention, positioning of the endface of the dielectric waveguide line in a transmission directionrelative to the input-output portion of the substrate can be achievedwith ease, wherefore connection between them can be established withoutcausing significant positional deviation. As a result, high-frequencyconnection between the circuit board and the substrate formed with theinput-output portion can be established stably with lower loss.

BRIEF DESCRIPTION OF DRAWINGS

Other and further objects, features, and advantages of the inventionwill be more explicit from the following detailed description taken withreference to the drawings wherein:

FIG. 1 is a diagram showing the structure of a high-frequency module inaccordance with a first embodiment of the invention;

FIG. 2A is a diagram showing the structure of a circuit board;

FIG. 2B is a diagram showing the structure of the circuit board;

FIG. 3 is a diagram showing the structure of a high-frequency module inaccordance with a second embodiment of the invention;

FIG. 4 is a diagram showing the structure of a high-frequency module inaccordance with a third embodiment of the invention;

FIG. 5 is a diagram showing the structure of the high-frequency module;

FIG. 6 is a diagram showing the structure of a transmitter in accordancewith a fourth embodiment of the invention;

FIG. 7 is a diagram showing the structure of a receiver in accordancewith a fifth embodiment of the invention; and

FIG. 8 is a diagram showing the structure of a transceiver and a radarapparatus in accordance with a sixth embodiment of the invention.

REFERENCE SIGNS LIST

-   -   1: Dielectric layer    -   2: Conductor layer    -   3: Through conductor    -   3 a: Through conductor group    -   4: Dielectric waveguide line    -   4 a: End face of a transmission direction    -   5: Circuit board    -   6: Waveguide    -   7: Substrate waveguide    -   7 a: First input-output port    -   7 b: Second input-output port    -   8: Antenna board    -   9: MMIC    -   10: Planar line    -   11: Bonding wire    -   12: Adjustment element    -   13: High-frequency wave reflection preventing portion    -   20, 21: High-frequency module    -   30: Transmitter    -   40: Receiver    -   50: Transceiver    -   60: Radar apparatus    -   100: High-frequency module    -   101 a: First cavity    -   101 b: Second cavity    -   102: Stacked waveguide line    -   102 a: Converting portion    -   105: Metal carrier layer    -   106: Electrically conductive bonding layer    -   108: Sealing structure    -   109: Control board    -   111: Control signal pad    -   112: High-frequency wave reflection preventing portion    -   120: Circuit board

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the drawings, preferred embodiments of the inventionare described below.

FIG. 1 is a diagram showing the structure of a high-frequency module 20in accordance with a first embodiment of the invention. Moreover, FIGS.2A and 2B are diagrams showing the structure of a circuit board 5. FIG.2A is a top view of the circuit board 5, and FIG. 2B is a side view ofthe circuit board 5 as viewed in a direction of high-frequency signaltransmission. The high-frequency module 20 includes the circuit board 5,a waveguide 6, and a substrate 8 having a first input-output portion (afirst input-output port 7 a) for high-frequency signals formed on onesurface thereof.

The circuit board 5 comprises a dielectric, layer 1, a pair of conductorlayers 2 opposed to each other, with the dielectric layer 1 lyingtherebetween, and a through conductor group 3 a that electricallyconnects the pair of conductor layers 2. The through conductor group 3 acomprises a plurality of through conductors 3 passing all the waythrough the dielectric layer 1 to establish electrical connectionbetween the pair of conductor layers 2. The through conductor group 3 acomprises a pair of arrays of through conductors spaced apart in thehigh-frequency signal transmission direction by a distance g. The pairedthrough conductor arrays are spaced apart in a direction perpendicularto the high-frequency signal transmission direction by a distance w.

The through conductor group 3 a thus placed forms electrical side walls,and the side walls and the pair of conductor layers 2 constitute adielectric waveguide line 4 acting as a waveguide.

Moreover, a plurality of dielectric waveguide lines 4 may be stacked ontop of each other in layers to construct a stacked waveguide line. Inthis case, the number of the layers may vary from part to part withinthe circuit board 5.

It is noted that the distance g is less than half the wavelength of ahigh-frequency signal. In this case, an electromagnetic wave being fedis transmitted through the dielectric waveguide line 4 in thehigh-frequency signal transmission direction while being reflectedwithout leaking from a gap between the through conductors. Moreover,although the distances g should preferably be secured at regularintervals, it is essential only that the distance g be less than halfthe wavelength of a high-frequency signal to be transmitted, whereforeit may be set arbitrarily so long as the above condition is fulfilled.

On the circuit board 5 shown in FIG. 1 are arranged a planar line 10 andan MMIC 9, which is a high-frequency circuit element, electricallyconnected to the planar line 10. The planar line 10 and the MMIC 9 areelectrically connected to each other through a bonding wire 11.

The planar line 10, the bonding wire 11, etc. constitute ahigh-frequency transmission line conductor which is electricallyconnected to the dielectric waveguide line 4, and the high-frequencytransmission line conductor and the dielectric waveguide line 4constitute a high-frequency transmission line that transmitshigh-frequency signals in a microwave band or a millimeter-wave band.

Therefore, a high-frequency signal outputted from the MMIC 9 istransmitted through the bonding wire 11 and along a surface of theconductor layer 2 from a connection part formed between the planar line10 and the bonding wire 11, and is further transmitted through thedielectric waveguide line 4. Note that a connection structure formedbetween the MMIC 9 and the planar line 10 does not necessarily have tobe the bonding-wire 11 connection structure, but may be of a flip-chipconnection structure.

In the circuit board 5 having the above-described connection structure,it is preferable that the dielectric layer 1 is made of ceramics fromthe viewpoints of precision with which to form a transmission line andeasiness of manufacture, although there is no particular limitation solong as a material whose properties do not interfere with transmissionof a high-frequency signal is used.

The dielectric layer 1 is obtained as follows. For example, a suitableorganic solvent is admixed in powder of a raw ceramic material such asglass ceramics, alumina ceramics, aluminum nitride ceramics, or the liketo prepare a slurry. The slurry is shaped into sheets by means ofheretofore known doctor blade technique, calender roll technique, orotherwise. Then, the sheet-like dielectric layer 1 is subjected to anappropriate punching process, and a conductor paste is charged into aresultant via-hole to thereby form the through conductor 3. Lastly, thesheet-like dielectric layer is fired at temperatures ranging from 850°C. to 1000° C. in the case of using glass ceramics, temperatures rangingfrom 1500° C. to 1700° C. in the case of using alumina ceramics, ortemperatures ranging from 1600° C. to 1900° C. in the case of usingaluminum nitride ceramics.

It is noted that a resin material can be used for the dielectric layer 1from the viewpoints of transmission signal frequency and manufacturingcost. Examples of the resin material which can be used for thedielectric layer 1 include fluorine resin, fluorine resin containing aglass base material, and an admixture material of inorganic particlesand resin.

Moreover, for example, when the dielectric layer 1 is made of aluminaceramics, the conductor layer 2 is formed as follows. Firstly aconductor paste prepared by admixing a suitable oxide such as alumina,silica, magnesia, etc. or an organic solvent in powder of metal such astungsten, molybdenum, etc. is printed onto the dielectric layer 1 by athick-film printing method. After that, co-firing is performed at atemperature as high as approximately 1600° C. so that the resultantconductor layer 2 can have a thickness of approximately 5 to 50 μm. Notethat, as the metal powder, powder of copper, gold, or silver isdesirable in the case of using glass ceramics, and powder of tungsten ormolybdenum is desirable in the case of using alumina ceramics oraluminum nitride ceramics.

The circuit board 5 of the high-frequency module 20 of the presentembodiment is placed at a side of the one surface of the substrate 8such that a virtual plane extending beyond an end face 4 a of thedielectric waveguide line 4 and the one surface of the substrate 8 wherethe first input-output port 7 a of the substrate 8 is exposed intersecteach other, and preferably intersect each other substantially at rightangles.

The substrate 8 has a substrate waveguide 7 formed so as to passtherethrough in its thickness direction. The substrate waveguide 7 hasthe first input-output port 7 a acting as the first input-output portionat a side of the one surface of the substrate 7 (where the circuit board5 is placed) and also has a second input-output port 7 b acting as asecond input-output portion at a side of the other surface thereof.Herein, an antenna board can be taken up as exemplary of the substrate8. Note that the substrate waveguide 7 may either be of a space or havea dielectric material charged therein.

In a case where the substrate 8 is an antenna board, a high-frequencysignal that has been outputted from the MMIC 9 and transmitted throughthe dielectric waveguide line 4, is transmitted through the waveguide 6which will hereafter be described to the first input-output port 7 a,and is transmitted therefrom through the substrate waveguide 7, and isradiated from the second input-output port 7 b. Moreover, ahigh-frequency signal acquired at the second input-output port 7 b istransmitted through the substrate waveguide 7 to the first input-outputport 7 a, is transmitted therefrom through the waveguide 6, and istransmitted through the dielectric waveguide line 4.

In this embodiment, the substrate 8 is an antenna board. In thehigh-frequency module 20 of this embodiment, by virtue of the positionalrelation such that the virtual plane of the end face 4 a of thedielectric waveguide line 4 and the one surface of the substrate 8intersect each other, connection between the end face 4 a of thedielectric waveguide line 4 and the waveguide 6, as well as connectionbetween the waveguide 6 and the first input-output port 7 a, can beestablished under a visible condition with high positional accuracy,with consequent reduction in positional deviation between the dielectricwaveguide line 4 and the first input-output port 7 a.

Moreover, although it is possible to interpose, between the circuitboard 5 and the substrate 8, a resin substrate or the like havingperipheral circuitry that is provided for signal transfer with thecircuit board 5, in the present embodiment, the circuit board 5 isfixedly mounted on the one surface of the substrate 8.

The waveguide 6 has a cavity thereinside and has openings at endsthereof. One of the openings is connected to the end face 4 a of thedielectric waveguide line 4, and the other thereof is connected to thefirst input-output port 7 a of the substrate 8. Moreover, since thevirtual plane of the end face 4 a of the dielectric waveguide line 4 islocated so as to be intersected by the one surface of the substrate 8,it follows that the waveguide 6 is configured to have bends to provideconnection between the end face 4 a of the dielectric waveguide line 4and the first input-output port 7 a of the substrate 8. With theprovision of such a waveguide 6 having bends to establish connectionbetween input-output portions that differ from each other in terms of ahigh-frequency signal transmission direction, a band of high-frequencysignals to be transmitted can be utilized extensively. Moreover, withinthe waveguide 6, a high-frequency signal can be transmitted under a modeconversion-free condition:

Moreover, a region lying between the end face 4 a of the dielectricwaveguide line 4 and the first input-output port 7 a of the substrate 8can be covered with the waveguide 6 properly, wherefore leakage of ahigh-frequency signal can be suppressed in the region lying between theend face 4 a and the first input-output port 7 a.

Moreover, the waveguide 6 may comprise grooves located on a periphery ofone of the openings at intervals of substantially a quarter of thewavelength of a high-frequency signal and having a width substantiallyequal to the interval. Since such a groove serves as a choke, it ispossible to suppress leakage of a high-frequency signal from a gap atthe connection part in the opening.

It is preferable that the waveguide 6 is formed of a metal tube made ofa metal such as aluminum. When the waveguide 6 is formed of a metaltube, heat dissipation can be improved, wherefore high-frequencyconnection between the circuit board 5 and the substrate 8 can beachieved stably with lower loss. Moreover, it is possible to constructthe waveguide 6 by applying a metal plating to an inner peripheralsurface of a resin tube. When the waveguide 6 is constructed by applyinga metal plating to an inner peripheral surface of a resin tube, thethickness of the metal plating is determined in consideration of skineffect.

Moreover, it is preferable to dispose a high-frequency wave preventingportion 13 at an upper corner of the bend of the waveguide 6. Thehigh-frequency is provided by bonding a triangle-prism member made ofthe same material as that of the waveguide 6 to the corner of thewaveguide 6, or by forming a corner of an inner wall of the waveguide 6into an inclined surface. This is intended to eliminate a right-anglecorner because, when the right-angle corner exists in the cavity of thewaveguide 6, an electric field concentrates at the corner and reflectionof high-frequency signals occurs. This makes it possible to prevent theelectric field concentration and prevent the reflection ofhigh-frequency signals. Therefore, high-frequency connection between thecircuit board 5 and the substrate 8 can be achieved stably with lowerloss.

FIG. 3 is a diagram showing the structure of a high-frequency module 21in accordance with a second embodiment of the invention. Thehigh-frequency module 21 is analogous to the above-describedhigh-frequency module 20, and thus like components will be identifiedwith the same reference symbols and overlapping descriptions will beomitted. In the high-frequency module 21, the waveguide 6 is providedwith pin-shaped adjustment elements 12 which are displaceable in each ofthe X-axis direction, the Y-axis direction, and the Z-axis directionwithin the cavity of the waveguide 6. By causing displacement of theadjustment elements 12 along a longitudinal direction thereof, thefrequency of a high-frequency signal to be transmitted through thewaveguide 6 can be adjusted. Note that the adjustment element 12 may beplaced along at least one of the X-axis direction, the Y-axis direction,and the Z-axis direction.

Next, a method of manufacturing the high-frequency module 20, 21 will bedescribed. To begin with, the circuit board 5 is put on the one surfaceof the substrate 8 and mounted thereon such that a virtual planeextending beyond the end face 4 a of the dielectric waveguide line 4 forhigh-frequency signals and the one surface of the substrate 8 where thefirst input-output port 7 a is exposed intersect each other, andpreferably intersect each other substantially at right angles. In thisway, the end face 4 a of the dielectric waveguide line 4 and the firstinput-output port 7 a of the substrate 8 serving as an input-outputportion during transmission of a high-frequency signal can be visuallychecked at the same time.

Then, the waveguide 6 is mounted, with its one end positioned andconnected with respect to the end face 4 a of the dielectric waveguideline 4 and the other end positioned and connected with respect to thefirst input-output port 7 a of the substrate 8. At this time, since theend face 4 a of the dielectric waveguide line 4 and the firstinput-output port 7 a of the substrate 8 can be visually checked at thesame time, it is possible to facilitate the positioning of the waveguide6 and thereby enhance positioning accuracy. Accordingly, in thehigh-frequency module 20, 21 manufactured by this manufacturing method,local variations of high-frequency signals can be suppressed at theconnection part formed between the waveguide 6 and the dielectricwaveguide line 4, as well as the connection part formed between thewaveguide 6 and the substrate waveguide 7, wherefore high-frequencyconnection between the circuit board 5 and the substrate 8 can beachieved stably with lower loss.

Moreover, the waveguide 6 is mounted on the substrate 8 after thecircuit board 5 is mounted on the substrate 8, with consequent greaterdesign flexibility in the structure of the waveguide 6. Specifically, itis possible to readily implement a structure in which a part of thewaveguide 6 is placed above the circuit board 5 so as to cover the endface 4 a of the dielectric waveguide line 4 from above. Accordingly, thehigh-frequency module 20, 21 manufactured by this manufacturing methodsucceeds in effectively suppressing high-frequency signal leakage at theend face 4 a of the dielectric waveguide line 4.

Another method of manufacturing the high-frequency module 20, 21 will bedescribed below. To begin with, the other of the openings of thewaveguide 6 is positioned and connected with respect to the openingplane of the first input-output port 7 a of the substrate 8. At thistime, since the first input-output port 7 a can be visually checked withease, it is possible to facilitate positioning and thereby connect theopenings with the first input-output port 7 a without causingsignificant positional deviation.

Then, the end face 4 a of the dielectric waveguide line 4 is positionedand connected with respect to one opening plane of the waveguide 6, andthe circuit board 5 is put on the one surface of the substrate 8 andmounted thereon. At this time, since the end face 4 a of the dielectricwaveguide line 4 can be visually checked with ease, it is possible tofacilitate positioning and thereby connect the opening with the firstinput-output port 7 a while minimizing positional deviation.

Accordingly, in the high-frequency module 20, 21 manufactured by thismanufacturing method, local variations of the transmission path overwhich a high-frequency signal is transmitted can be suppressed in theinput-output portion, wherefore high-frequency connection between thecircuit board 5 and the substrate 8 can be achieved stably with lowerloss.

Moreover, since the circuit board 5 is mounted after the waveguide 6 ismounted at the side of one surface of the substrate 8, it follows that aclearance exists between the waveguide 6 and the circuit board 5immediately after the mounting of the circuit board 5. In this state, itbecomes possible to sort out conforming items, for example, reworkingcan be performed after conducting characterization in this state or theclearance between the waveguide 6 and the circuit board 5 can be coveredwith a conductor to obtain a finished assembly.

FIG. 4 is a sectional view showing the structure of a high-frequencymodule 100 in accordance with a third embodiment of the invention. FIG.5 is a front view showing the structure of the high-frequency module100. In this embodiment, the same components as those in the precedingembodiment will be identified with the same reference symbols, and thedescription thereof will be omitted. The high-frequency module 100includes a circuit board 120, the substrate 8 (antenna board) having thefirst input-output port 7 a formed on one surface thereof, and a sealingstructure 108 serving as a waveguide.

The circuit board 120 is a board in which a planar line 10 and a stackedwaveguide line 102, which is a dielectric waveguide line formed withinthe dielectric layer 1, are electrically connected to each other therebyforming a high-frequency circuit. The planar line 10 is one of lines fortransmission of high-frequency signals in a microwave band or amillimeter-wave band, and is more specifically designed to transmithigh-frequency signals through a wiring conductor. Although a microstripline and a coplanar line can be taken up as exemplary of the planar line10, a microstrip line is preferable for use.

The stacked waveguide line 102 is basically similar in structure to thedielectric waveguide line 4 shown in FIGS. 2A and 2B, and its outer endsurface is rendered as an input-output portion in an exposed state forthe input and output of high-frequency signals.

In the circuit board 120 of the present embodiment, the dielectric layer1 includes a first cavity 101 a and a second cavity 101 b which isformed inside the first cavity 101 a and is smaller than the firstcavity 101 a. On the bottom surface of the first cavity 101 a, viz., aregion lying around the second cavity 101 b, is disposed a convertingportion 102 a. On the bottom surface of the second cavity 101, the MMIC9, etc. which is a semiconductor device is mounted.

A high-frequency signal outputted from the MMIC 9 is transmitted throughthe bonding wire 11 to the planar line 10, and further through theconverting portion 102 a and is transmitted through the stackedwaveguide line 102.

Meanwhile, the substrate 8 of the present embodiment is an antenna boardhaving a plurality of substrate waveguides 7. Moreover, on the substrate8 is disposed a control board 109 that controls transmission andreception of high-frequency signals in the substrate 8. The controlboard 109 and the circuit board 120 are electrically connected to eachother via a control signal pad 111.

The sealing structure 108 is provided to protect a semiconductor devicesuch as the MMIC 9 from damage by temperature, humidity, and mechanicalloss, and is thus formed so as to cover the entire circuit board 120. Asurface of the circuit board 120 and an inner surface of the sealingstructure 108 make intimate contact with each other, and a space iscreated between a lateral surface of the circuit board 120 and an innerlateral surface of the sealing structure 108. The space constitutes awaveguide 6. The first input-output port 7 a of the substrate waveguide7 is connected via the waveguide 6 to an end face of the stackedwaveguide line 102.

Therefore, a high-frequency signal that has been outputted from the MMIC9 and transmitted through the stacked waveguide line 102, is transmittedthrough the waveguide 6 of the sealing structure 108 to the firstinput-output port 7 a, and is transmitted therefrom through thesubstrate waveguide 7, and is radiated from the second input-output port7 b. Moreover, a high-frequency signal acquired at the secondinput-output port 7 b is transmitted through the substrate waveguide 7to the first input-output port 7 a, and is transmitted therefrom throughthe waveguide 6, and is transmitted through the stacked waveguide line102.

Just as is the case with the preceding embodiment, it is preferable todispose a high-frequency wave reflection preventing portion 112 at theupper corner of the waveguide 6.

In the present embodiment, the sealing structure 108 is made of a metalmaterial such as aluminum. When it is made of a metal material in thatway, the sealing structure 108 that covers the circuit board 120functions to dissipate heat evolved from a semiconductor device such asthe MMIC 9 to the outside, wherefore characteristic degradation of thesemiconductor device can be suppressed.

As described heretofore, the high-frequency module 100 of the presentembodiment is so designed that the input-output portion for the inputand output of high-frequency signals in the circuit board 120 conformsto the outer end face of the stacked waveguide line 102, and the endface of the stacked waveguide line 102 and the first input-output port 7a of the substrate 8 are connected to each other by the waveguide 6 ofthe sealing structure 108. In this construction, the lateral surface ofthe circuit board can be utilized effectively, and an undesirableincrease in the size of the circuit board 120 can be prevented, comparedwith a case where a circuit board and a substrate are arranged such thatan input-output portion of the circuit board and an input-output portionof the substrate are opposed to each other, wherefore miniaturizationcan be achieved.

Moreover, the downsized circuit board 120 makes it possible to reducethe size of the sealing structure 108 that covers the circuit board 120.Correspondingly, the internal space of the sealing structure 108 thataccommodates a semiconductor device such as the MMIC 9 can be evensmaller. This makes it possible to prevent induction of an unnecessaryresonance phenomenon in the internal space and thereby preventcharacteristic degradation of a semiconductor device such as the MMIC 9.

Moreover, the input-output portion of the stacked waveguide line 102 andthe first input-output port 7 a of the substrate 8 are connected to eachother by the waveguide 6, wherefore a band of high-frequency signals tobe transmitted can be utilized extensively. Moreover, the waveguide 6 isdisposed at the connection part formed between the input-output portionof the stacked waveguide line 102 and the first input-output port 7 a ofthe substrate 8, wherefore a high-frequency signal can be transmittedwithin the waveguide 6 under a mode conversion-free condition.

Moreover, in the high-frequency module 100 of the present embodiment,the circuit board 120 is fixedly mounted on the one surface of thesubstrate 8 through an electrically conductive bonding layer 106 suchthat the end face of the stacked waveguide line 102 acting as theinput-output portion and the one surface of the substrate 8 where thefirst input-output port 7 a is exposed intersect each other, andpreferably intersect each other substantially at right angles. At thistime, between the circuit board 120 and the substrate 8 is formed ametal carrier layer 105 that maintains shielding between the board andthe substrate. The sealing structure 108 is fixedly mounted on thedielectric layer 1, which is the uppermost layer of the circuit board120, through an electrically conductive bonding layer 106 so as to coverthe circuit board 120 and the first input-output port 7 a of thesubstrate 8. In this construction, a space surrounded by the sealingstructure 108, the lateral surface of the circuit board 120, and thesubstrate 8 can be created, and this space serves as the cavitywaveguide 6. In this way, the structure of the high-frequency module 100can be simplified.

Further, since the space surrounded by the first and second cavitiesformed in the circuit board 120 and the sealing structure 108 and thespace corresponding to the waveguide 6 are spaced away from each other,it is possible to prevent intrusion of a high-frequency wave beingtransmitted in the space of the waveguide 6 into the space at the sideof the cavity, as well as intrusion of a radiation wave radiated fromthe bonding wire 11 or the MMIC 9 in the space at the side of the cavityinto the space of the waveguide 6.

Next, a transmitter, a receiver, a transceiver, and a radar apparatuscomprising the high-frequency module 100 will be described. FIG. 6 is adiagram showing the structure of a transmitter 30 in accordance with afourth embodiment of the invention. The transmitter 30 of thisembodiment comprises the high-frequency module 100. The transmitter 30includes an oscillator 31 that produces high-frequency signals mountedon one surface of the circuit board 120. The oscillator 31 is connectedvia the planar line 10 to the stacked waveguide line 102. Thetransmitter 30 is configured to radiate a high-frequency signal producedby the oscillator 31 from an antenna (the second input-output port 7 b)at the side of the other surface of the substrate 8 (antenna board).

Moreover, FIG. 7 is a diagram showing the structure of a receiver 40 inaccordance with a fifth embodiment of the invention. The receiver 40 ofthis embodiment comprises the high-frequency module 100. The receiver 40comprises a wave detector 41 mounted on one surface of the circuit board120. The wave detector 41 is connected via the planar line 10 to thestacked waveguide line 102. The receiver 40 detects a high-frequencysignal acquired at the antenna (the second input-output port 7 b) of thesubstrate 8 (antenna board) by means of the wave detector 41.

Further, FIG. 8 is a diagram showing the structure of a transceiver 50and a radar apparatus 60 in accordance with a sixth embodiment of theinvention. The radar apparatus 60 of this embodiment includes thetransceiver 50 comprising the high-frequency module 100, and a detector61 that detects at least a distance to an object to be detected orrelative velocity on the basis of an intermediate-frequency signal froma mixer 53 disposed in the transceiver 50.

The transceiver 50 comprises the high-frequency module 100. Thetransceiver 50 includes an oscillator 31, a branch 51, and a mixer 53.The oscillator 31 is mounted on one surface of the circuit board 120 andis connected to the planar line 10. Moreover, the branch 51 is disposedin the planar line 10 to branch a high-frequency signal produced by theoscillator 31. One of the high-frequency signals branched by the branch51 is radiated from an antenna (the second input-output port 7 b)through a divider 52. The second input-output port 7 b also acts toacquire a high-frequency signal. The mixer 53 mixes the other of thehigh-frequency signals branched by the branch 51 and a high-frequencysignal which has been acquired at the second input-output port 7 b andtransmitted thereto through the divider 52 and outputs anintermediate-frequency signal.

According to the transmitter 30, the receiver 40, the transceiver 50,and the radar apparatus 60 thus far described, with the provision of thehigh-frequency module 100, the placement of the oscillator 31, the wavedetector 41, etc. on one surface of the circuit board 120, and theplacement of the substrate 8 for transmission and reception, etc. on theother surface of the circuit board 120, it is possible to, in aneffective manner, transmit a high-frequency signal processed in thehigh-frequency circuit forming section at the side of the one surface tothe substrate 8 disposed at the side of the other surface and thenradiate it from the second input-output port 7 b on the other surface ofthe substrate 8, as well as to transmit a high-frequency signal acquiredat the second input-output port 7 b of the substrate 8 disposed at theside of the other surface to the high-frequency circuit forming sectionat the side of the one surface of the circuit board 120. Accordingly,both miniaturization and excellent transmission-reception performancecapability can be achieved.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and the rangeof equivalency of the claims are therefore intended to be embracedtherein.

1. A high-frequency module, comprising: a substrate comprising aninput-output portion for high-frequency signal formed on one surfacethereof; a circuit board comprising a dielectric waveguide line with itsend face exposed, the circuit board being located on the one surface ofthe substrate such that a virtual plane extending beyond the end faceintersects with the one surface of the substrate; and a waveguidecomprising openings at both ends thereof, one of the openings beingconnected to the end face of the dielectric waveguide line, and theother of the openings being connected to the input-output portion of thesubstrate.
 2. The high-frequency module according to claim 1, whereinthe one surface of the substrate and the virtual plane intersect witheach other substantially at right angles.
 3. The high-frequency moduleaccording to claim 1, wherein the waveguide further comprises grooveslocated on a periphery of one of the openings at intervals ofsubstantially a quarter of a wavelength of the high-frequency signal andhaving a width which is substantially equal to a length of one of theintervals.
 4. The high-frequency module according to claim 1, whereinthe circuit board further comprises a mounting portion configured tomount a semiconductor device thereon, a planar line configured toelectrically connect to the semiconductor device, and a convertingportion configured to convert the high-frequency signal transmissionfrom the planar line to the dielectric waveguide line.
 5. Thehigh-frequency module according to claim 4, wherein the mounting portionand the converting portion are located in a cavity formed in the circuitboard.
 6. The high-frequency module according to claim 1, furthercomprising a sealing structure covering an end face of the dielectricwaveguide line of the circuit board, with a space secured between thesealing structure and the end face, wherein a part of the sealingstructure which covers the end face of the dielectric waveguide line isconfigured to be the waveguide.
 7. The high-frequency module accordingto claim 6, wherein the sealing structure is configured to cover theinput-output portion of the substrate, and a space surrounded by aninner surface of the sealing structure, a lateral surface of the circuitboard, and the one surface of the substrate is configured to be aninternal space of the waveguide.
 8. A method of manufacturing ahigh-frequency module, comprising: preparing a substrate comprising aninput-output portion for high-frequency signal formed on one surfacethereof, a waveguide comprising openings at both ends thereof and havinga relationship such that a virtual opening plane extending beyond one ofthe openings is intersected by a virtual opening plane extending beyondthe other of the openings, and a circuit board comprising a dielectricwaveguide line exposed at an end face thereof; disposing the circuitboard at a side of the one surface of the substrate; and mounting thewaveguide on the substrate such that the one of the openings of thewaveguide is connected to the end face of the dielectric waveguide lineand the other of the openings of the waveguide is connected to theinput-output portion of the substrate.
 9. A method of manufacturing ahigh-frequency module, comprising: preparing a substrate comprising aninput-output portion for high-frequency signal formed on one surfacethereof, a waveguide comprising openings at both ends thereof and havinga relationship such that a virtual opening plane extending beyond one ofthe openings is intersected by a virtual opening plane extending beyondthe other of the openings, and a circuit board comprising a dielectricwaveguide line exposed at an end face thereof; mounting the waveguide onthe substrate such that the other of the openings is connected to theinput-output portion; and mounting the circuit board on the substratesuch that the end face of the dielectric waveguide line is connected tothe one of the openings of the waveguide.
 10. A transmitter, comprising:the high-frequency module according to claim 4; an oscillator configuredto produce the high-frequency signal, the oscillator being mounted onthe circuit board and connected to the planar line; and an antennaconfigured to radiate the high-frequency signal produced by theoscillator, the antenna being located at a side of the other surface ofthe substrate and connected to the dielectric waveguide line.
 11. Areceiver comprising: the high-frequency module according to claim 4; anantenna configured to acquire the high-frequency signal, the antennabeing located at a side of the other surface of the substrate andconnected to the dielectric waveguide line; and a wave detectorconfigured to detect the high-frequency signal acquired by the antenna,the wave detector being mounted on the circuit board and connected tothe dielectric waveguide line.
 12. A transceiver, comprising: thehigh-frequency module according to claim 4; an oscillator configured toproduce the high-frequency signal, the oscillator being mounted on thecircuit board and connected to the planar line; a branch configured tobranch the high-frequency signal produced by the oscillator, the branchbeing located in the planar line; a transmitting antenna configured toradiate one of the high-frequency signals branched by the branch, thetransmitting antenna being located at a side of the other surface of thesubstrate and connected to the dielectric waveguide line; a receivingantenna configured to acquire the high-frequency signal, the receivingantenna being located at the side of the other surface of the substrateand connected to the dielectric waveguide line; and a mixer configuredto mix the other of the high-frequency signals branched by the branchand a high-frequency signal acquired by the receiving antenna and outputan intermediate-frequency signal.
 13. A radar apparatus, comprising: thetransceiver according to claim 12; and a detector configured to detect adistance to an object to be detected or a relative velocity with theobject, on a basis of the intermediate-frequency signal from the mixer.